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Monday, 31 January 2011

Wireless Friendly Buildings

Long back I wrote about problems with Radiation Proofed homes. Since then the wireless technologies have got more popular and the technologies in infancy have become mainstream.

Last week I heard Professor Richard Langley from Sheffield University speaking on the topic of wireless friendly buildings. The problem now is manifold rather than just keeping the wireless signal in or out.

Think about the WiFi that is installed in nearly every house. The signals from WiFi are best kept indoors to avoid the interference to neighbours. Wifi uses 2.4GHz ISM band. On the other hand we may want the mobile signal to penetrate the house so that we can get good reception. In Europe UMTS is mostly 2.1GHz and LTE may be mostly 2.6GHz. The intention of the building should be to keep the WiFi signal out and the UMTS/LTE signal in.

The problem we have to remember is that with the frequencies going higher, the penetration of signals are becoming a problem. This means that the construction of the buildings should be modified to keep the attenuation to minimum, higher the frequency.

With femtocells most likely to become more popular by the day, you may want to keep these frequencies from going out of the house but allowing them to come in. This presents a big challenge. The intention of the buildings design in the western world is to keep the cold/heat/radiation out. The concept of 'wireless friendly building design' is the least important in the mind of the architects and civil engineers.

The may change over the time due to effort by the organisations like the Wireless Friendly Building Forum (WFBF).

From an article in Building.co.uk:

At the moment, says Chris Yates, chairman of the Wireless Friendly Building Forum (WFBF), predicting the performance of a building to handle wireless signals is almost impossible. “There is a lot of spurious science around and software that purports to give plots of wireless coverage in a building. It’s utterly naive and doesn’t reflect reality,” he says.

One of the reasons the forum was set up at the end of last year was to co-ordinate research into the area of wireless systems in buildings. As the use of wireless devices increases, more and more issues over performance will arise, explains Yates - and there is nobody taking an interdisciplinary approach on how this performance can be improved.

With wireless looking set to be a mainstay of the way we work in the future, the WFBF ultimately wants to develop a way of defining and assessing its performance in any one building, similar to the way in which BREEAM or LEED rate a building’s environmental performance. “Then a value can be placed on it and developers and end users get interested and it becomes part of their decision-making process,” says Yates.

But until this is achieved, what should designers be doing? Here, we take a look at three wireless applications and the main implications for buildings.

Cellular signals are broadcast by public masts and are actually very difficult to keep out of a building. The main path in is through the glazing, but once inside, things can start to go haywire, with signals reflected or absorbed by the building’s structure.

Columns, lift shafts and risers in particular can create blackspots where reception becomes poor or non-existent. Concrete floors cast on lightweight metal decks will block most signals, as will materials such as lead roofing and the metal foils on the back of some insulation materials.

A common way to deal with this is to boost the signal or re-broadcast it using a repeater. These systems usually use an external antenna to collect the signal, which is transmitted to an amplifier and retransmitted locally. For multistorey buildings, several transmitters might be needed.

Of course, this equipment needs to be accommodated and installed, but when this should be done is a source of some confusion. The current BCO guide to specification does not outline at what stage ICT infrastructure should be installed, but according to Yates some sort of infrastructure provision should be made at the core and shell stage, even if the active equipment isn’t installed.

Signal strength can also be significantly decreased by the use of high-performance glazing and solar shading, which are becoming commonplace with the tightening of Part L of the Building Regulations.

Mitigating action can be taken. Buro Happold’s specialist facade division, for example, is now beginning to consider the effect that facade components have on wireless performance, while also considering trade-offs in acoustic, blast, thermal performance and aesthetics.

According to Yates these trade-offs need careful consideration. Some glass options might give marginally better performance in terms of thermal behaviour, but completely ruin the wireless service, whereas another option might give negligible degradation for a similar price. “

So it is something to think about. It’s no good handing the building over and then telling them there’s no wireless signal,” warns Yates.

The following is an interesting presentation on the related topic:

Saturday, 29 January 2011

Making of the Qualcomm Museum



For Qualcomm, Baker created a corporate museum experience that gives visitors an understanding of what lies at the core of the company’s extraordinary success story.


Thursday, 27 January 2011

Attocell: Smaller Femtocell

Over the last year Femtocells et al. have been slowly rebranded as Small cells and I agree that it is a much more generic term and easier for end users to understand.

Last year, around this time, magicJack announced a small USB Femtocell (a lot of Femto manufacturers disagree that its a Femtocell) that can help reduce the cost of call and just a few days back Picochip announced picoXcell, a USB form factor femtocell.

Yesterday, Ubiquisys announced the Attocell. As can be seen in the picture above, in mathematics, femto is 10^-15 and atto is 10^-18. I know that some of you may think that there is still scope for zeptocells and yoctocells but it may be difficult to see in the light of Attocells, what they can be.

A few years back, I blogged about how Femtocells can be used to steal the spectrum. Well, Attocell legally allows to do just that. The press release states the following:

The attocell connects to a user’s laptop via USB, which provides power and an internet connection. It then analyses the IP address and radio environment to determine which country it is in, and sets its 3G radio power accordingly to below the licenced level. In some countries its range will be just 5mm, in other countries, it could cover a whole room.

Like Ubiquisys femtocells, the attocell continuously monitors its radio environment to ensure that there is zero impact on existing mobile networks. This intelligence, combined with its tiny power output, is likely to make the attocell exempt from regulatory controls and the requirement for type approval.

In 5mm mode, the traveller simply lays the iPhone on top of the device and the phone connects automatically, just like a regular femtocell. Calls can be made using a Bluetooth or wired headset , or by using the iPhone’s speaker.

You can understand more by reading the official Attocell FAQ here.

It would be very interesting to see if any of the big operators support this device. Roaming revenues are big part of operators profit. Informa has predicted that this roaming revenue will keep rising. The roaming revenue comes from voice, sms as well as data. Some business users in one business trip frequently shell as much as a personal user would for a years contract. So its not really in operators interest to promote these devices.

On the other hand, small operators and MVNO may really like this as this can help them win more subscribers and can be the differentiators in the market.

Once more thing worth remembering is that since the arrival of Skype, the occasional and cautious mobile users have no hesitation on making VoIP calls and keeping friends, family and colleagues back home up to date with their status. The operators are aware of this and wouldnt mind the users instead using their mobiles via attocell.

Ubiquisys will show the Attocell in MWC in mid-Feb and we will have to wait and see the reaction.

Wednesday, 26 January 2011

Tuesday, 25 January 2011

MAPCON - Multi Access PDN Connectivity

On Monday, I read Bernard Herscovich, CEO, BelAir Networks saying the following in RCR Wireless:

Wi-Fi is obviously a way to offload data to alleviate congestion, but it also contributes to overall network profitability by delivering data at a lower cost per megabit that traditional macrocells. ABI Research estimates that carrier Wi-Fi can deliver data at 5% the cost of adding cellular capacity. Perhaps the most important driver, though, is the fact that, properly designed and architected, a carrier Wi-Fi network will deliver a consistently great user experience. The implications of that on attracting and retaining subscribers are obvious.

We've also seen cable operators taking advantage of their broadband HFC infrastructure to mount Wi-Fi APs throughout their coverage areas, offering free Wi-Fi as a sticky service to attract and retain home broadband subscribers.

At the GSMA Mobile Asia Congress, back in mid-November, 2010, KDDI's president and chairman explained that while they would be migrating to LTE, which would double their network capacity, data demand in Japan was forecast to increase by 15 times over the next five years. So LTE alone, he admitted, would not be enough. A few weeks before that, European operators, including Deutsche Telekom and Telefonica, were making similar statements at the Broadband World Forum in Paris.

It is clear that LTE alone will not be sufficient to meet ongoing mobile data demand. Technical innovation has resulted in huge capacity gains, but we're now at a point where additional bandwidth is more of a by-product of incremental spectrum. And, we all realize the finite nature of that resource. So, based on this new spectrum, LTE macrocells could deliver a 2 – 4X capacity increase. Meanwhile, ABI estimates that data capacity requirements are increasing 150% per year.

So, it's pretty clear that carriers are going to need more than just an LTE swap out to keep delivering a great user experience. They need to, as many already realize, augment their licensed spectrum with Wi-Fi. KT, the second largest mobile carrier in South Korea, claims to be offloading 67% of their mobile data traffic onto Wi-Fi. There may also be additional unlicensed spectrum made available, at least in the U.S. and the U.K., through the release of so-called white space spectrum, freed up through the switch from analog to digital TV.

It is obvious from the technology point of view that Multiple PDN connections would need to be supported when the UE is using LTE for part of data connection and Wi-Fi for other part. In fact these two (or multiple) connections should be under the control of the same EPC core that can help support seamless mobility once you move out of the WiFi hotspot.

One of the items in 3GPP Release-10 is to do with supporting of multiple Packet Data Networks (PDN) connections for a device. A Release-9 network and the UE can only support 3GPP access based connection via EPC. In Release-10 support for upto 1 non-3GPP access has been added.

FMC100044 specifies the following requirements:

  • The Evolved Packet System supports the following scenarios: a single Operator offering both fixed and mobile access; different Operators collaborating to deliver services across both networks.
  • The Evolved Packet System shall support the access of services from mobile network through fixed access network via interworking.
  • The Evolved Packet System shall be able to support functions for connectivity, subscriber authentication, accounting, Policy Control and quality of service for interworking between the fixed broadband access and Evolved Packet Core.
  • The Evolved Packet System shall optimize QoS and Policy management meaning that it shall offer minimal signalling overhead, while interworking between the fixed broadband access and Evolved Packet Core.
  • The Evolved Packet System shall be able to provide an equivalent experience to users consuming services via different accesses.

The Rel-10 work item extends Rel-9 EPC to allow a UE equipped with multiple network interfaces to establish multiple PDN connections to different APNs via different access systems. The enhancements enable:

  • Establishment of PDN connections to different APNs over multiple accesses. A UE opens a new PDN connection on an access that was previously unused or on one of the accesses it is already simultaneously connected to.
  • Selective transfer of PDN connections between accesses. Upon inter-system handover a UE transfers only a subset of the active PDN connections from the source to the target access, with the restriction that multiple PDN connections to the same APN shall be kept in one access.
  • Transfer of all PDN connections out of a certain access system. A UE that is simultaneously connected to multiple access systems moves all the active PDN connections from the source to target access, e.g. in case the UE goes out of the coverage of the source access.

This work also provides mechanisms enabling operator's control on routing of active PDN connections across available accesses.

The scope of the work is restricted to scenarios where the UE is simultaneously connected to one 3GPP access and one, and only one, non-3GPP access. The non-3GPP access can be either trusted or untrusted.

The design of the required extensions to Rel-9 EPC is based on TR 23.861 Annex A, that provides an overview of the changes that are expected in TS 23.401 and TS 23.402 for the UE to simultaneously connect to different PDNs via different access systems.

See Also:

3GPP TR 23.861: Multi access PDN connectivity and IP flow mobility

3GPP TS 22.278: Service requirements for the Evolved Packet System (EPS)

Old Blog post on Multiple PDN Connectivity

Monday, 24 January 2011

Simplified view of Heterogeneous Networks (HetNets)

A very simple picture explaining HetNets are,

To learn more about HetNet's, see my old blog post here or the Qualcomm video from yesterday here.

Saturday, 22 January 2011

Wilson Street: What can femtocells do - the next big thing!

I have blogged about the Alcatel-Lucent (ALU) Femtocells in the past. Few months back I posted about their shift from using the term Femtocells to Small cells. To make everyone aware of this small cells they launched their Wilson Street experiment and are now producing some episodes to show how these small cells can play big part in everyday life.

The first two episodes are embedded below from Youtube.






The latest (3rd) episode is available on the Wilson Street Website here.

Thursday, 20 January 2011

eMPS: Enhanced Multimedia Priority Service in Release-10 and beyond


The response to emergency situations (e.g., floods, hurricanes, earthquakes, terrorist attacks) depends on the communication capabilities of public networks. In most cases, emergency responders use private radio systems to aid in the logistics of providing critically needed restoration services. However, certain government and emergency management officials and other authorised users have to rely on public network services when the communication capability of the serving network may be impaired, for example due to congestion or partial network infrastructure outages, perhaps due to a direct or indirect result of the emergency situation.

Multimedia Priority Service, supported by the 3GPP system set of services and features, is one element creating the ability to deliver calls or complete sessions of a high priority nature from mobile to mobile networks, mobile to fixed networks, and fixed to mobile networks.

Requirements for the Multimedia Priority Service (MPS) have been specified in TS 22.153 for the 3GPP Release-9

The intention of MPS is to enable National Security/Emergency Preparedness (NS/EP) users (herein called Service Users) to make priority calls/sessions using the public networks during network congestion conditions. Service Users are the government-authorized personnel, emergency management officials and/or other authorized users. Effective disaster response and management rely on the Service User’s ability to communicate during congestion conditions. Service Users are expected to receive priority treatment, in support of mission critical multimedia communications.

LTE/EPC Release 9 supports IMS-based voice call origination by a Service User and voice call termination to a Service User with priority. However, mechanisms for completing a call with priority do not exist for call delivery to a regular user for a priority call originated by a Service User. MPS enhancements are needed to support priority treatment for Release 10 and beyond for call termination and for the support of packet data and multimedia services.

MPS will provide broadband IP-based multimedia services (IMS-based and non-IMS-based) over wireless networks in support of voice, video, and data services. Network support for MPS will require end-to-end priority treatment in call/session origination/termination including the Non Access Stratum (NAS) and Access Stratum (AS) signaling establishment procedures at originating/terminating network side as well as resource allocation in the core and radio networks for bearers. The MPS will also require end-to-end priority treatment in case of roaming if supported by the visiting network and if the roaming user is authorized to receive priority service.

MPS requirement is already achieved in the 3G circuit-switched network. Therefore, if the network supports CS Fallback, it is necessary to provide at least the same capability as 3G circuit switched-network in order not to degrade the level of voice service. In CS Fallback, UE initiates the fallback procedures over the LTE as specified in TS 23.272 when UE decides to use the CS voice service for mobile originating and mobile terminating calls. To achieve priority handling of CS Fallback, NAS and AS signaling establishment procedures, common for both IP-based multimedia services and CS Fallback, shall be treated in a prioritized way.

In Release-10, for LTE/EPC, the following mechanisms will be specified.
  • Mechanisms to allocate resources for signaling and media with priority based on subscribed priority or based on priority indicated by service signaling.
  • For a terminating IMS session over LTE, a mechanism for the network to detect priority of the session and treat it with priority.
In Release-10, for CS Fallback, the following mechanism will be specified:
  • A mechanism to properly handle the priority terminating voice call and enable the target UE to establish the AS and NAS connection to fall-back to the GERAN/UTRAN/1xRTT.
For more information, see:

3GPP TR 23.854: Enhancements for Multimedia Priority Service (Release 10)

3GPP TS 22.153: Multimedia priority service (Release 10)

Tuesday, 18 January 2011

3GPP Tutorials via 'The SpecTools'

Some of you may have noticed that the new and revamped 3GPP website have recently started offering 3GPP specs and features tutorials via The SpecTools. There is quite a lot of useful information and most of it is premium but a lot is free as well.

So the new starters or those wishing to refresh their knowledge feel free to check this out:

Monday, 17 January 2011

Heterogeneous LTE Networks and Inter-Cell Interference Coordination

An interesting paper that is more of a background to my earlier post here is available from Nomor Research and is embedded below.
This paper is available to download from here.

Thursday, 13 January 2011

RAN mechanisms to avoid CN overload due to MTC

Machine-to-Machine (M2M) is the future and Machine-type communications (MTC) will be very important once we have billions of connected devices. I have talked in the past about the 50 Billion connected devices by 2050 and the Internet of Things.

One of the challenges of today's networks is to handle this additional signalling traffic due to MTC. One of the very important topics being discussed in 3GPP RAN meetings is 'RAN mechanisms to avoid CN overload due to MTC'. Even though it has not been finalised, its interesting to see the direction in which things are moving.

The above figure from R2-106188 shows that an extended wait time could be added in the RRC Connection Reject/Release message in case if the eNodeB is overloaded. The device can reattempt the connection once the wait time has expired.


In R2-110462, another approach is shown where Core Network (CN) is overloaded. Here a NAS Request message is sent with delay tolerant indicator a.k.a. low priority indicator. If the CN is overloaded then it can reject the request with a backoff timer. Another approach would be to send this info to the eNodeB that can do a RRC Connection Reject when new connection request is received.

All Documents from 3GPP RAN2 #72-bis are available here. Search for NIMTC for M2M related and overload related docs.

Tuesday, 11 January 2011

Monday, 10 January 2011

SI on Signalling and procedure for interference avoidance for in-device coexistence

In order to allow users to access various networks and services ubiquitously, an increasing number of UEs are equipped with multiple radio transceivers. For example, a UE may be equipped with LTE, WiFi, and Bluetooth transceivers, and GNSS receivers. One resulting challenge lies in trying to avoid coexistence interference between those collocated radio transceivers. Figure 4-1 below shows an example of coexistence interference.


3GPP initiated a Study Item (SI) in Release-10 timeframe to investigate the effects of the interference due to multiple radios and signalling. This study is detailed in 3GPP TR 36.816 (see link at the end).

Due to extreme proximity of multiple radio transceivers within the same UE, the transmit power of one transmitter may be much higher than the received power level of another receiver. By means of filter technologies and sufficient frequency separation, the transmit signal may not result in significant interference. But for some coexistence scenarios, e.g. different radio technologies within the same UE operating on adjacent frequencies, current state-of-the-art filter technology might not provide sufficient rejection. Therefore, solving the interference problem by single generic RF design may not always be possible and alternative methods needs to be considered. An illustration of such kind of problem is shown in Figure 4-2 above.

The following scenarios were studied:
- LTE coexisting with WiFi
- LTE coexisting with Bluetooth
- LTE Coexisting with GNSS

Based on the analysis in SI, some examples of the problematic coexistence scenarios that need to be further studied are as follows:
- Case 1: LTE Band 40 radio Tx causing interference to ISM radio Rx;
- Case 2: ISM radio Tx causing interference to LTE Band 40 radio Rx;
- Case 3: LTE Band 7 radio Tx causing interference to ISM radio Rx;
- Case 4: LTE Band 7/13/14 radio Tx causing interference to GNSS radio Rx.

In order to facilitate the study, it is also important to identify the usage scenarios that need to be considered. This is because different usage scenarios will lead to different assumption on behaviours of LTE and other technologies radio, which in turn impact on the potential solutions. The following scenarios will be considered:

1a) LTE + BT earphone (VoIP service)
1b) LTE + BT earphone (Multimedia service)
2) LTE + WiFi portable router
3) LTE + WiFi offload
4) LTE + GNSS Receiver

The SI also proposes some ways of reducing the interference and is work in progress at the moment.

Reference: 3GPP TR 36.816 : Study on signalling and procedure for interference avoidance for in-device coexistence; (Release 10).

Sunday, 9 January 2011

Dilbert Humour: Cloud Computing

Source: Dilbert

If you like these then please click 'Very Useful' or 'More like this' so that I know people find these useful.

For similar things follow the label: Mobile Humour.

Friday, 7 January 2011

LTE-Advanced (Rel-10) UE Categories

I blogged about the 1200Mbps of DL with LTE Advanced earlier and quite a few people asked me about the bandwidth, etc. I found another UE categories table in Agilent lterature on LTE-Advanced here.

The existing UE categories 1-5 for Release 8 and Release 9 are shown in Table 4. In order to accommodate LTE-Advanced capabilities, three new UE categories 6-8 have been defined.


Note that category 8 exceeds the requirements of IMT-Advanced by a considerable
margin.

Given the many possible combinations of layers and carrier aggregation, many configurations could be used to meet the data rates in Table 4. Tables 5 and 6 define the most probable cases for which performance requirements will be developed.

Thursday, 6 January 2011

Refresher: LTE MAC Layer Protocol

This is following the RLC refresher post here. You can also view logs from real tests on a real LTE UE here.

Wednesday, 5 January 2011

eICIC: Enhanced inter-cell interference coordination in 3GPP Release-10

Inter-cell interference coordination (ICIC) was introduced in Release-8/9 of the 3GPP LTE standards. The basic idea of ICIC is keeping the inter-cell interferences under control by radio resource management (RRM) methods. ICIC is inherently a multi-cell RRM function that needs to take into account information (e.g. the resource usage status and traffic load situation) from multiple cells.

Broadly speaking, the main target of any ICIC strategy is to determine the resources (bandwidth and power) available at each cell at any time. Then (and typically), an autonomous scheduler assigns those resources to users. Thus, from the Radio Resource Control perspective, there are two kind of decisions: (a) which resources will be allocated to each cell? and, (b) which resources will be allocated to each user?. Clearly, the temporality of such decisions is quite different. Whereas resources to users allocation is in the order of milliseconds, the allocation of resources to cells take much longer periods of time or can be fixed.

Static ICIC schemes are attractive for operators since the complexity of their deployment is very low and there is not need for new extra signaling out of the standard. Static ICIC mostly relies on the fractional reuse concept. This means that users are categorized according to their Signal-to-Noise-plus-Interference Ratio (SINR), that means basically according to their inter-cell interference, and different reuse factors are applied to them, being higher at regions with more interference, mostly outer regions of the cells. The total system bandwidth is divided into sub-bands which are used by the scheduler accordingly.

A simple way to explain ICIC is based on picture above. The users are divided into two categories, one is Cell Center User (CCU), and the other one is Cell Edge User (CEU). CCUs are the users distributed in the gray region of above figure, and CEUs are the users distributed in the above red, green and blue areas. CCU can use all the frequencypoints to communicate with the base station, while CEU must use corresponding specified frequency points to ensure orthogonality between different cells.
CEUs can be assigned a higher transmissionpower for the frequency reuse factor is greater than 1. The frequency points are not overlapped at the edges so the adjacent cell interference is small. CCU’s frequency reuse factor is 1; for the path loss is small and transmission power is low. Therefore the interference to the adjacent cells is not high either.

Dominant interference condition has been shown when Non-CSG/CSG users are in close proximity of Femto, in this case, Rel8/9 ICIC techniques are not fully effective in mitigating control channel interference, and hence, Enhanced interference management is needed At least the following issues should be addressed by any proposed solutions:
o Radio link monitoring (RLM)
o Radio Resource Management (including detection of PSS/SSS and PBCH)
o Interference from CRS
oo To PCFICH/PHICH/PDCCH
oo To PDSCH
o CSI measurement
o Interference from PDCCH masked with P-RNTI and SI-RNTI (for SIB-1 only) and associated PCFICH

As a result, from Release-10 onwards eICIC work was started. In Rel-10, two eICIC or Enhanced inter-cell interference coordination (also incorrectly referred to as Enhanced Inter-Cell Interference Cancellation) were being actively discussed. They are Time domain eICIC and autonomous HeNB power setting. More advanced ideas are being thought of beyong Rel-10 including Interference management techniques on carrier resolution ( optimally exploiting available Networks frequency assets (carriers in same or different bands) , combination with Carrier Aggregation; interference management schemes proposed both during LTE-Advanced Study Item phase, and during Rel-10 HetNet eICIC work.

From an earlier presentation in SON Conference:

eICIC:
- Effectively extends ICIC to DL control - time domain
- Requires synchronization at least between macro eNB and low power eNBs in its footprint
- No negative impact on legacy Rel 8 Use

Range Extension(RE)
- Refers to UE ability to connect and stay connected to a cell with low SINR
- Achieved with advanced UE receivers - DL interference cancellation (IC)

RE + eICIC technique:
– Eliminates coverage holes created by closed HeNBs
– Improves load balancing potential for macro network with low power eNBs and leads to significant network throughput increase
–Enables more UEs can be served by low power eNBs, which can lead to substantially higher network throughput

More details on eICIC is available in 3GPP CR's and TR's listed below:
  • R1-105081: Summary of the description of candidate eICIC solutions, 3GPP TSG-WG1 #62, Madrid, Spain, August 23rd – 27th, 2010.
  • R1-104942: Views on eICIC Schemes for Rel-10, 3GPP TSG RAN WG1 Meeting #62, Madrid, Spain, 23-27 August, 2010.
  • R1-104238: eICIC Chairman’s note, 3GPP TSG RAN WG1 Meeting #61bis, Dresden, Germany, 28th June – 2nd July 2010.
  • R1-103822: Enhanced ICIC considerations for HetNet scenarios, 3GPP TSG RAN WG1 #61bis Meeting, Dresden, Germany, June 28 – July 2, 2010.
You can also check out NTT Docomo's presentation on LTE Enhancements and Future Radio Access here.

Tuesday, 4 January 2011

Mobile Broadband Enablers in future

From a presentation by Huawei at the New Zealand Future Wireless Technologies Seminar. The presentation is available here.